The present invention is generally directed to toner processes, and more specifically, to aggregation and coalescence processes for the preparation of toner compositions. In embodiments, the present invention is directed to the economical preparation of toners without the utilization of the known pulverization and/or classification methods, and wherein in embodiments toner compositions with a volume average diameter of from about 1 to about 25, and preferably from 1 to about 10 microns, and narrow GSD of, for example, from about 1.16 to about 1.26 as measured on the Coulter Counter can be obtained. The resulting toners can be selected for known electrophotographic imaging, printing processes, including color processes, and lithography. In embodiments, the present invention is directed to a process comprised of dispersing a pigment and optionally toner additives like a charge control agent or additive in an aqueous mixture containing an ionic surfactant in an amount of from about 0.5 percent (weight percent throughout unless otherwise indicated) to about 10 percent, and shearing this mixture with a certain latex or emulsion mixture comprised of suspended submicron resin particles of from, for example, about 0.01 micron to about 2 microns in volume average diameter in an aqueous solution containing a counterionic surfactant in amounts of from about 1 percent to about 10 percent with opposite charge to the ionic surfactant of the pigment dispersion, and nonionic surfactant in amounts of from about 0 percent to about 5 percent, thereby causing a flocculation of resin particles, pigment particles and optional charge control agent, followed by heating at about 5.degree. to about 40.degree. C. below the resin Tg and preferably about 5.degree. to about 25.degree. C. below the resin Tg while stirring of the flocculent mixture, which is believed to form statically bound aggregates of from about 1 micron to about 10 microns in volume average diameter comprised of resin, pigment and optionally charge control particles, and thereafter heating the formed bound aggregates about above the Tg (glass transition temperature) of the resin. The size of the aforementioned statistically bonded aggregated particles can be controlled by adjusting the temperature in the below the resin Tg heating stage. An increase in the temperature causes an increase in the size of the aggregated particle. This process of aggregating submicron latex and pigment particles is kinetically controlled, that is, the temperature increases the process of aggregation. The higher the temperature during stirring the quicker the aggregates are formed, for example from about 2 to about 10 times faster in embodiments, and the latex submicron particles are picked up more quickly. The temperature also controls in embodiments the particle size distribution of the aggregates, for example the higher the temperature the narrower the particle size distribution and this narrower distribution can be achieved in, for example, from about 0.5 to about 24 hours and preferably in about 1 to about 3 hours time. Heating the mixture about above or in embodiments equal to the resin Tg generates toner particles with, for example, an volume average particle diameter of from about 1 to about 25 and preferably 10 microns. It is believed that during the heating stage, the components of aggregated particles fuse together to form composite toner particles.
Of importance with respect to the present invention is the selection of a latex mixture comprised of three or more monomers, one of which is vinyl halide, such as vinyl chloride, a vinylidene halide, such as vinylidene chloride, or mixtures thereof. Monomers present in the latex include, for example, four monomers such as styrene, butyl acrylate, acrylic acid and vinylidene chloride. With such monomers, there are enabled toner polymer resin binders that enhance negative charging of the toner. For example, the negative charge on the toner with a polymer resulting from the four monomer mixture of styrene, butyl acrylate, vinylidene chloride and acrylic acid is generally from about 15 .mu.C/gram to about 25 .mu.C/gram before any external additives are included onto the toner; when only styrene, butylacrylate and acrylic acid monomers are used, tribocharging of the resultant toner is from about 10 to about 15 .mu.C/gram.
In embodiments thereof, the present invention is directed to an in situ process comprised of first dispersing a pigment, such as HELIOGEN BLUE.TM. or HOSTAPERM PINK.TM., in an aqueous mixture containing a cationic surfactant, such as benzalkonium chloride (SANIZOL B-50.TM.), Utilizing a high shearing device, such as a Brinkmann Polytron, microfluidizer or sonicator, thereafter shearing this mixture with a latex of suspended resin particles, such as poly(styrene butadiene-vinylidene chloride-acrylic acid), and which particles are, for example, of a size ranging from about 0.01 to about 0.5 micron in volume average diameter as measured by the Brookhaven nanosizer in an aqueous surfactant mixture containing an anionic surfactant, such as sodium dodecylbenzene sulfonate, for example NEOGEN R.TM. or NEOGEN SC.TM., and a nonionic surfactant, such as alkyl phenoxy poly(ethyleneoxy)ethanol, for example IGEPAL 897.TM. or ANTAROX 897.TM., thereby resulting in a flocculation, or heterocoagulation of the resin particles with the pigment particles; and which, on further stirring for about 1 to about 3 hours while heating, for example, from about 35.degree. to about 45.degree. C., results in the formation of statically bound aggregates ranging in size of from about 0.5 micron to about 10 microns in average diameter size as measured by the Coulter Counter (Microsizer II), where the size of those aggregated particles and their distribution can be controlled by the temperature of heating, for example from about 5.degree. to about 25.degree. C. below the resin Tg, and where the speed at which toner size aggregates are formed can also be controlled by the temperature. Thereafter, heating from about 5.degree. to about 50.degree. C. above the resin Tg provides for particle fusion or coalescence of the polymer and pigment particles, followed by optional washing with, for example, hot water to remove surfactant, and drying whereby toner particles comprised of resin and pigment with various particle size diameters can be obtained, such as from 1 to about 20, and preferably 12 microns in volume average particle diameter. The aforementioned toners are especially useful for the development of colored images with excellent line and solid resolution, and wherein substantially no background deposits are present.
There is illustrated in U.S. Pat. No. 4,996,127 a toner of associated particles of secondary particles comprising primary particles of certain polymers having acidic or basic polar groups and a coloring agent. The polymers selected for the toners of the '127 patent can be prepared by an emulsion polymerization method, see for example columns 4 and 5 of this patent. In column 7 of this '127 patent, it is indicated that the toner can be prepared by mixing the required amount of coloring agent and optional charge additive with an emulsion of the polymer having an acidic or basic polar group obtained by emulsion polymerization. Also, see column 9, lines 50 to 55, wherein a polar monomer, such as acrylic acid, in the emulsion resin is necessary, and toner preparation is not obtained without the use, for example, of an acrylic acid polar group, see Comparative Example I. In U.S. Pat. No. 4,983,488, there is disclosed a process for the preparation of toners by the polymerization of certain polymerizable monomers dispersed by emulsification in the presence of a colorant and/or a magnetic powder to prepare a principal resin component, and then effecting coagulation of the resulting polymerization liquid in such a manner that the particles in the liquid after coagulation have diameters suitable for a toner.
Emulsion/aggregation processes for the preparation of toners are illustrated in a number of Xerox patents, the disclosures of which are totally incorporated herein by reference, such as U.S. Pat. No. 5,290,654, U.S. Pat. No. 5,278,020, U.S. Pat. No. 5,308,734, U.S. Pat. No. 5,346,797, U.S. Pat. No. 5,370,963, U.S. Pat. No. 5,344,738, U.S. Pat. No. 5,403,693, U.S. Pat. No. 5,418,108, U.S. Pat. No. 5,364,729, and U.S. Pat. No. 5,346,797.